Four years after his disappearance, police have received about 15,000 pieces of information about William Tyrell.
Photograph: Nsw Police/PR IMAGE

It was almost a year ago when detective chief inspector Gary Jubelin last spoke to the media on the third anniversary of the disappearance of William Tyrrell.

At the time, Jubelin was defiant police were “not giving up” on the investigation into what happened to the three-year-old boy in the Spiderman suit who vanished from his grandmother’s front yard on the New South Wales mid north coast in 2014.

On Wednesday, Jubelin, the officer who has led the investigation and has previously admitted the case “weighed heavily” on him, came as close as ever to conceding the likelihood of finding Tyrrell alive was increasingly slim.

He told media in Kendall on Wednesday that police held “grave, grave fears” about William, who was three when he disappeared.

“It’s been a very long time,” he said.

“As I’ve said to the family, and I can’t be any more honest than what I say to the family ... until we know conclusively that William is not alive we’ll treat it with the possibility that he still is alive. But obviously we have grave concerns.”

Four years after his disappearance, police have received some 15,000 pieces of information about William and sifted through hundreds of persons of interest.

On Wednesday they started afresh, returning to the street where William disappeared to begin a “forensic” search of bushland surrounding the home.

Police returning to search for evidence in the area surrounding William Tyrrell’s home. Photograph: Joel Carrett/AAP

Jubelin said the search was about establishing that William’s disappearance “was “the result of human intervention and not through misadventure”, before a possible coronial inquest.

“The difference between this search and the search that was done originally [is that] the original search was focused on finding a little boy lost,” he said.

“The search commencing today, which we anticipate will take between three to four weeks, will be focusing on a forensic search.

“The purpose of this is that if we present evidence to a court, whether coronial or criminal, [we can show] beyond reasonable doubt that William’s disappearance was the result of human intervention and not through misadventure.”

The first day of the search saw about 50 officers cover some 600 sq metres using shovels and trowels to comb through bushland while dogs searched the area. The search will continue for another four weeks until an area of 3 sq km has been covered.

The case has enveloped the small town of Kendall, near Port Macquarie on the NSW mid-north coast. When Tyrrell first disappeared it sparked one of the largest searches in NSW police history.

In the 10 days following his disappearance hundreds of police and community members combed through bushland but nothing was found. Theories about the case have come and gone.

On Wednesday Jubelin said that this had still not been totally ruled out as a line of inquiry, but it had not led to any charges.

“Until this matter is solved, we keep all lines of inquiry open,” he said.

But still no arrests have been made.

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For locals, the disappearance is baffling. William’s grandmother lived on a secluded cul-de-sac well away from the Pacific Highway that Kendall straddles, and neighbours keep a close eye on one another.

“It’s just weird to me,”Lisa Reimer, who lives on the street said.

“When my kids [are] outside playing you’re thinking how could it happen. It’s big open yards [and] you hear every car and noise.”

Reimer only moved to Kendall six months ago, but her parents have lived here for more than a decade. She said visitors always stood out.

“If I was visiting they [the neighbours] all knew that I was up,” she said.

“You look in the yards and think how could someone sneak up there, it just makes no sense.”